Hydraulic engine with compact brake

ABSTRACT

A hydraulic motor ( 1 ) comprising a casing ( 2 A,  2 B) a reaction member having a reaction profile ( 4 ), a cylinder block ( 6 ), an internal fluid distributor ( 16 ) suitable for putting the cylinders ( 12 ) of the cylinder block ( 6 ) in communication with fluid feed and exhaust ducts, and a braking system which comprises first and second braking elements ( 42, 44 ), constrained to rotate respectively with the reaction member ( 4 ) and with the cylinder block ( 6 ). The braking system further comprises a brake piston ( 40 ) suitable for being displaced axially so as to urge the braking elements into braking contact or so as to enable braking to be released. The brake piston is constrained to rotate with the casing about the axis of rotation, and it has a substantially radial active face, a first brake member ( 42 ) belonging to the first braking means being integral with said active face.

The present invention relates to a hydraulic motor comprising:

a casing;

a reaction member integral with or secured to the casing and having aninternal periphery that defines a reaction profile; and

a cylinder block which is mounted so that the cylinder block and thereaction member rotate relative to each other about an axis of rotation,the cylinder block comprising a plurality of piston-and-cylinder setsdisposed radialy relative to the axis of rotation and suitable for beingfed with fluid under pressure;

an internal fluid distributor constrained to rotate with the casingabout the axis of rotation, and provided with distribution ducts thatcan put the cylinders in communication with fluid feed and exhaustducts; and

a braking system comprising first and second braking means constrainedto rotate respectively with the casing and with the cylinder block aboutthe axis of rotation, a brake piston suitable for taking up both abrake-releasing position and a braking position in which it urges thefirst and second braking means into braking engagement so as to preventthe cylinder block and the casing from rotating relative to each other,and means for displacing the brake piston between said braking andbrake-releasing positions.

The invention applies more particularly to motors in which the brakeacts as a parking brake or as a safety brake, i.e. in which the brakeacts without dissipating energy and below a predetermined speed, whichvaries depending on the embodiment, and which is about 100 revolutionsper minute (r.p.m.) on average.

In known motors of the above-mentioned type, the first braking means aregenerally constituted by a first series of brake pads in the form ofrings which are secured to a portion of the casing referred to as the“brake casing”, via axial fluting. The brake casing is fixed to theother portions of the casing by screws or any other suitable securingmeans. The second braking means are constituted by a second series ofbrake pads in the form of rings interposed between the pads of the firstseries, and constrained to rotate with a brake shaft by means of axialfluting. The brake shaft is itself constrained to rotate with thecylinder block by means of fluting. The brake piston is disposed in thebrake casing, at one end thereof. It is generally urged in the brakingdirection by a spring washer, and it is hydraulically displaced in thebrake-releasing direction by means of a fluid under pressure containedin a brake release chamber.

Such known systems are generally satisfactory but they suffer fromseveral drawbacks.

Firstly, they are made up of quite a large number of parts that aredifficult to assemble together. In addition, during braking or duringbrake release, the piston can “slip” relative to the brake disk that isclosest to it. Furthermore, brake disks are subjected to considerablestress from the braking torque. They must be extremely strong in theregion of the fluting, in which region the stresses are extremely highbecause of the smallness of the contact areas between the fluting on thedisks and the fluting on the part (the brake casing or the brake shaft)to which they are secured.

An object of the invention is to improve known systems so as to providesafe and effective braking with a small number of parts, or, at least,with parts whose dimensioning and method of assembly are such that theymake it possible to limit the manufacturing cost of the “brake” portionof the motor.

This object is achieved by the fact that the brake piston is constrainedto rotate with the casing about the axis of rotation and it has asubstantially radial active braking face, a first brake member belongingto the first braking means being integral with or secured to said activeface.

As described below, constraining the brake piston to rotate with thecasing may be achieved by keying it by means of coupling profilesprovided with fluting, or, preferably, with undulations which are freefrom sharp edges or angles. The undulations form a curve whose tangentcan be determined at all points. The brake piston is a part ofrelatively large dimensions (in particular of large thickness), so thatachieving the keying poses no particular difficulty.

The brake piston or the coupling profiles can easily be organized towithstand high braking torque. The first brake member is integral withor secured to the active face of the piston, which means that it iseither directly constituted by said active face, or it is machined insaid active face, or else it is formed by a separate part (a series ofteeth of a positive clutch, or a first brake pad) which is fixed to saidactive face by any known means.

In which case, it is easy to choose the fixing means, e.g. welding, sothat they withstand the braking torque. In addition, it is easy toensure that the contact areas between the first brake member and thebraking piston are relatively large (these areas are formed on radialfaces), so that the stresses to which the coupling between the firstbrake member and the piston is subjected on braking are proportionallyless high than the stresses to which the coupling between the first diskand the part (casing or brake shaft) with which it is constrained torotate is subjected in conventional systems.

Advantageously, the first and second braking means respectively comprisea first series of positive clutch teeth and a second series of positiveclutch teeth, the first series of teeth being integral with or securedto the active face of the brake piston.

In which case, motor manufacture and motor assembly are made evensimpler. The first series of teeth may be machined directly on theactive face of the brake piston, or else they may be provided on anannular ring, itself fixed to the brake piston. Similarly, the secondseries of teeth may be machined directly on a radial face of thecylinder block or on some other part that is prevented from rotatingrelative to the cylinder block, or else they may be formed on an annularring fixed to the cylinder block or to some other part. In addition, theforces involved on braking, which forces affect the first braking means(first series of teeth) are transmitted in full to the casing by meansof the brake piston being constrained to rotate with said casing.

Preferably, the motor includes a coupling collar which forms a portionof the casing and which has an internal axial face with which anexternal axial face of the brake piston co-operates to key said pistonso that it is constrained to rotate with the casing, said internal andexternal axial faces having coupling profiles suitable for this purpose.

The coupling collar is advantageously directly adjacent to the reactionmember and it may even be constituted by an axial extension of thereaction member, which extension is integral with said reaction member.

In which case, the coupling profile of the internal axial face of thecoupling collar is chosen to be analogous to the reaction profile. Thus,since the reaction member is correctly dimensioned to transmit the drivetorque, it is guaranteed that the members via which the braking torquepasses are also correctly dimensioned. In addition, the machining of thecoupling profile formed on the internal axial face of the couplingcollar is simplified because it makes use of at least some of the lobesof the cam.

The coupling collar may also be constituted by an annular part which isinterposed between the reaction member and the “distribution cover”portion of the casing, which portion surrounds the distributor. In whichcase, it is very simple to fix the coupling collar to the other portionsof the casing. In addition, the brake piston is then situated in anannular space provided around the distributor under the collar, so thatthe overall axial size of the motor is reduced. Even in this case, it isadvantageous to machine the internal periphery of the coupling collar ina manner such that it is provided with undulations whose trough portionscorrespond to at least some of the trough portions of the reactionmember. This simplifies firstly the angular keying of the couplingcollar relative to the reaction member on assembling the casing of themotor. In addition, the undulations in the coupling collar are thennaturally dimensioned such that they withstand the high braking torque.

In general, it is advantageous for the coupling collar to be disposed ina manner such that its coupling profile is situated within the axialspace occupied by some other part of the motor. In the above-indicatedconfiguration, this profile lies within the axial space occupied by thedistributor. In another advantageous variant, the coupling collar may bedisposed on the other side of the cylinder block from the distributor,it then being possible for its coupling profile to lie within the axialspace occupied by some other part, such as a roller bearing forsupporting the casing as it rotates relative to the shaft or to thecylinder block.

It is extremely advantageous to make provision to ensure that theportion of the piston that co-operates with the casing (the couplingcollar) to constrain the piston to rotate with the casing is distantfrom the axis of the motor. For example, it may be situatedsubstantially in axial alignment with the reaction profile. The brakingtorque exerted between the piston and the casing increases as a functionof increasing distance between the axis of the rotation of the motor andthe mutually-cooperating surfaces (coupling profiles) of the casing andof the piston.

By making provision for these surfaces to be in a region distant fromthe axis, it is possible to obtain high braking torque with stressesthat are lower than those involved in the prior art. This alsoconstitutes an advantage, in particular in terms of braking reliability,and in terms of resistance to wear.

To the same end, it is advantageous to make provision to ensure that thebraking means (e.g. the teeth of the positive clutch) via which thebraking torque passes are situated in a large-diameter region of themotor, thereby considerably limiting the risks of the parts of the motorwearing prematurely or breaking.

The invention will be well understood, and its advantages will appearmore clearly on reading the following detailed description ofembodiments given by way of non-limiting example and with reference toaccompanying drawings, in which:

FIG. 1 is an axial section view of a motor according to the invention;

FIGS. 2 to 5 are fragmentary axial section views showing variants of themotor shown in FIG. 1;

FIG. 6 is a diagrammatic radial section view on line VI—VI of FIG. 1,showing a variant;

FIG. 7 is a fragmentary axial section view showing another variant ofthe motor of FIG. 1;

FIG. 8 is a fragmentary axial section view showing yet another variant;

FIG. 9 is an axial section view of another embodiment of a motoraccording to the invention; and

FIG. 10 is a fragmentary axial section view of a variant embodiment ofthe motor shown in FIG. 9.

FIG. 1 shows a hydraulic motor which includes:

a stationary casing in two portions 2A and 2B, assembled together bymeans of screws 3;

a reaction member constituted by an undulating reaction cam 4 providedon the portion 2A of the casing;

a cylinder block 6 mounted to rotate relative to the cam 4 about an axisof rotation 10, and comprising a plurality of radial cylinders 12 whichare suitable for being fed with fluid under pressure, and in whichpistons 14 are slidably mounted; and

an internal fluid distributor 16 constrained to rotate with the casingabout the axis 10, and provided with distribution ducts 18 suitable forcommunicating with the cylinders 12.

Grooves 22 and 24 are provided between the internal distributor 16 andthe portion 2B of the casing, which portion forms a distribution cover.The distribution ducts open out firstly in one of the grooves (the duct18 opens out in the groove 22), and secondly in the distribution face 26of the internal distributor, which face is perpendicular to the axis 10and abuts against the communication face 28 of the cylinder block. Thecylinder ducts 30 open out in said communication face 28 and they aredisposed so that they can be put in communication with the distributionducts when the internal distributor and the cylinder block rotaterelative to each other.

The motor shown has only one operating cylinder, only two grooves beingprovided between the portion 2B of the casing and the internaldistributor 16. The grooves are themselves respectively connected toducts 32 and 34 which open out in an external face of the casing 2B soas to be connected to a hydraulic fluid circuit. Depending on therotation direction of the motor, the ducts 32 and 34 may perform a fluidfeed function or a fluid exhaust function. Conical roller bearings 36support the cylinder block so that it can rotate relative to the portion2A of the casing.

It is to be understood that the invention also applies to a motor havinga plurality of distinct operating cylinders.

Leakage return ducts 33A and 33B are also provided in the portion 2B ofthe casing.

The motor having a stationary casing as shown in FIG. 1 has no shaftdistinct from the cylinder block. That end face 6A of the cylinder blockwhich is further from the portion 2B of the casing constitutes theoutlet of the motor, and, by means of tapped holes suitable forco-operating with screws (not shown), this end of the cylinder block canbe fixed directly to an object to be driven in rotation.

The cylinder block is not bored through, but rather it has a transversewall 6B which closes off the inside space of the motor from the outside,the inside space being sealed with a sealing gasket 38.

Naturally, this cylinder block configuration merely constitutes anexample, and it is possible to provide some other configuration, with ashaft being constrained to rotate with the cylinder block by means ofaxial fluting.

The motor 1 further includes a braking system which comprises a brakepiston 40 having a radial end face (its “active face”) which is providedwith first braking means constituted by a first series of teeth 42 of apositive clutch, while the second braking means 44 are constituted bythe second series of teeth of the positive clutch, which series isintegral with or secured to a radial end face 46 of the cylinder block6, which face is situated facing the radial end face of the piston 40.The series of teeth 42 and 44 thus face each other, and it can beunderstood that, when the piston is displaced towards the cylinderblock, they engage one another so as to brake the cylinder blockrelative to the casing-and-cam assembly, i.e. so as to prevent thecylinder block from moving relative to said assembly. When the piston 40is moved away from the cylinder block, the teeth are in thebrake-releasing position, and they enable the cylinder block 6 to rotaterelative to the casing 2A. The teeth of the series 42 and 44 areangularly positioned radially and they form axially-extending pieces ofrelief.

Since it is integral with or secured to the end face 46 of the cylinderblock, the second series of teeth 44 is naturally constrained to rotatewith the cylinder block about the axis 10. In order to constrain thefirst series of teeth 42 to rotate with the casing of the motor, thatportion 2A of the casing which carries the cam is provided with an axialextension 48 forming a coupling collar which has an axial segmentforming a first coupling segment 47 that has an internal periphery thatdefines an internal profile 50 analogous to the profile of the cam 4.For example, the internal profile 50 may be identical to the profile ofthe cam 4 and, as shown in FIG. 1, merely consists of an axial extensionto the surface of the cam 4 beyond the end face 46 of the cylinder block6.

In order to co-operate with the internal profile 50, the brake piston 40is provided with a second coupling segment 52 which, on its externalaxial face, defines an external profile 54 which matches the internalprofile 50. When the motor is assembled, the piston is disposed so thatthe second coupling segment 52 is disposed inside the first couplingsegment 47, the external profile 54 co-operating with the internalprofile 50 to constrain the brake piston 40 to rotate with the portion2A of the casing.

For example, the internal profile may be identical to the reactionprofile, and constitute an axial extension thereto, while the externalprofile may be exactly complementary to the internal profile.

In FIG. 1, the brake piston 40 and the axial extension 48 of thereaction member, in which extension the first coupling segment 47 isprovided, are situated on that side of the cylinder block 6 which facesthe internal fluid distributor 16.

The braking system is thus formed substantially without increasing theoverall axial size of the motor, because the brake piston 40 is disposedin an annular cavity 56 provided above the internal distributor 16,under the portion 2A of the casing. In a variant, it is possible tochoose to dispose the brake piston on the other side of the cylinderblock, thereby increasing the overall axial size of the motor somewhat.This variant can however be advantageous, e.g. when the bearings thatsupport the cylinder block so that it can rotate relative to the casingare provided in separate parts that are fixed respectively to thecylinder block and to the casing.

Concerning the roller bearings 36, it should be noted that the examplegiven in FIG. 1 shows conical roller bearings, in place of which it maybe preferred to use bearings having spherical balls rolling in tracksand having four contact points, which also constitutes an advantage fromthe axial compactness point of view.

In order to cause the brake piston 40 to be displaced in thebreak-releasing direction, the motor is provided with a brake releasechamber 60 which is suitable for being fed with a fluid under pressurevia a brake release duct 62.

This chamber has a substantially radial wall which is formed by a face60A of the piston, which face faces the same way as the active face ofsaid piston (the active face being the face which carries the series ofteeth 42) and is offset axially relative to the active face (away fromthe second series of teeth 44).

The brake release chamber is formed between two stepped portions,respectively 48A and 48B, belonging to the axial extension 48 of thereaction member, and two stepped axial portions, respectively 40A and40B, belonging to the brake piston. The external periphery of the axialportion 40A co-operates with the internal profile of the axial portion48A, the sliding contact between said internal periphery and saidexternal periphery being sealed by a sealing gasket 64. Similarly, theexternal axial periphery of the portion 40B co-operates with theinternal axial periphery of the portion 48B, this sliding contact beingsealed by a second sealing gasket 66.

In the example shown in FIG. 1, the portion 40A of the pistonconstitutes the second coupling segment 52, and the portion 48A of theaxial extension 48 carries the internal profile 50 of the first couplingsegment 47. The profiles 50 and 54 thus act both as transmissionsurfaces for transmitting the braking torque (to this end, they haveprofiles identical or analogous to the profile of the cam) and also asguiding surfaces for guiding the piston as it slides, while being sealedfrom each other by means of gasket 64. In the example shown in FIG. 1,in order to make this sealed contact possible, the internal profile 50and the external profile 54 are exactly complementary, i.e. they havethe same undulations of complementary shape and interfitting snugly withone another with almost no clearance. For example, the gasket 64 may bedisposed in a groove provided in the profile 54, and its shape alsoreproduces the undulations of the internal and external profiles, withconstant thickness.

The external profile of the portion 40B of the piston 40 and theinternal periphery of the portion 48B of the axial extension 48 arecylindrical and have no undulations, their radius being slightly greaterthan the largest radius of the cam profile. In the top half of FIG. 1,the axial section includes the summit of a convex portion of the cam, inwhich portion the radius of said cam is at its minimum. It can be seenthat, at this place, the chamber 60 has radial walls, respectively 60Aand 60B of relatively large dimensions. In the bottom half of FIG. 1,the section includes the bottom of a concave surface of the cam, inwhich surface the radius of the cam is at its maximum, and it can beseen that the radial walls 60A and 60B of the chamber are almostnonexistent in this region. For example, the gasket 66 may be disposedin a groove provided in the external periphery of the portion 40B of thepiston and, insofar as it is to provide sealing between two cylindricalsurfaces, it is of the conventional ring shape.

When the chamber 60 is fed with fluid under pressure, said fluid tendsto push the piston back in the brake-releasing direction because of theforces that it exerts respectively on the radial walls 60A and 60B. Thepiston is returned in the braking direction by a spring washer 68 whichbears firstly against the brake release casing 2B, and secondly againstthat face of the piston which faces away from the cylinder block.

FIG. 2 shows a variant embodiment which makes it possible to avoidgiving one of the gaskets that seals the brake release chamber anundulating shape. This figure uses the same references as those in FIG.1, plus 100. The brake release chamber 160 is formed between the axialportions 148A and 148B of the coupling collar formed by the axialextension 148 and the axial portions 140A and 140B of the brake piston140. However, the external peripheries of the portions 140A and 140B, aswell as the internal peripheries of the portions 148A and 148B arecylindrical, the staggering between the axial portions giving thechamber radial walls 160A and 160B that are of constant heightthroughout the chamber. To achieve this, the first axial portion 148A ofthe axial extension 148 (the portion that is closer to the cylinderblock 106) is connected to the first coupling segment 147 via a setback148C which forms the transition between the undulating shape of theinternal profile 150 constituting the internal periphery of the couplingsegment 147 and the cylindrical shape of the internal periphery of theportion 148A. Similarly, the first axial portion of the brake piston140A is connected to the second coupling segment 152 via a shoulder 140Cwhich forms the transition between the undulating shape of the externalprofile 154 formed by the external periphery of the coupling segment 152and the cylindrical external periphery of the portion 140A. Thus, thegaskets 164 and 166 which seal the brake release chamber are ofconventional ring shape.

The setback 148C and the shoulder 140C may be present only in theregions corresponding to the convex zones of the cam 104, it beingpossible for the radius of the cylindrical surfaces of the internalperiphery of the portion 148A and of the external periphery of theportion 140A to be substantially equal to the maximum radius of the camat the bottoms of its concave zones.

In the variant shown in FIG. 3, the motor is organized to have a throughcentral recess. A configuration of this type is particularlyadvantageous for certain applications, in particular for those in whichthe motor is used to drive a drill bit, in which case the through recessin the motor constitutes a passageway via which the drilling mud isremoved. This configuration is also particularly advantageous when it isnecessary to provide a passageway for members of plant or tools drivenby means of the motor, e.g. for pipes conveying fluid or compressed air.It is particularly advantageous to use a motor of this type for drivingthe compacting rollers of an earth compactor, by making use of thepresence of the axial recess to dispose the shaft of a secondary motor.

FIG. 3 uses the same references as in FIG. 1, plus 200.

To form the axial passageway or central recess 270, the cylinder block206 is provided with a through axial bore 272. That portion of the motorwhich is distant from the axis 210 is not shown in FIG. 3, and thecylinder block is supported to rotate in the same way as in FIG. 1. Oncethe axial bore 272 has been provided, the problem consists in closingand sealing the inside space of the motor. For this purpose, a hollowcylindrical sleeve 274 is disposed in the internal distributor 216 sothat it extends beyond both of the axial ends of said distributor. Moreprecisely, the hollow cylindrical sleeve is provided with a first axialend 274A which is situated on the side of the distributor that facestowards the cylinder block 206, and which is connected in sealed mannerto the wall of the axial bore 272 of the cylinder block. For thispurpose, a sealing gasket 276 is disposed between the axial face of thebore 272 and that external axial face 275 of the sleeve 274 which issituated facing said face of the bore.

On the other side of the distributor 216, the second axial end 274B ofthe sleeve 274 is connected in sealed manner to the wall of an axialbore 278 which passes through the casing or, more precisely, through thepotion 202B thereof. Thus, the inside space of the motor is sealedrelative to the axial passageway 270. The sleeve 274 may be keyedaxially by means of its end 274A co-operating in abutment with ashoulder 273 provided in the bore 272 of the cylinder block. On theother end, abutment keying may be performed by any suitable means using,for example, the shoulder 274C of the external axial face of the sleeve.

In FIG. 4, the numerical references are the same as those used in FIG.1, plus 300. FIG. 4 shows an advantageous configuration in which theteeth of the braking positive clutch are used to measure the speed ofrotation of the rotor of the motor relative to its stator. For thispurpose, a speed detector 380 is received in an element of the stator ofthe motor, and it faces that one of the first and second series of teethwhich is constrained to rotate with the rotor of the motor.

In the example shown, the cylinder block belongs to the rotor and it isthus the second series of teeth 344 that faces the detector 380 in orderto measure the speed at which the teeth of the second series go past.The detector is received in a bore provided in the portion 302B of thecasing of the motor. The detector 380 is keyed by means of a ring 382,the bore in which it is received being sealed by means of gaskets 384.At its end situated outside the casing of the motor, it may be connectedto electrical cables. For example, it may be an optical system or anelectromagnetic system. Generally, any system suitable for transmittinga pulse each time a tooth goes past its sensor, so as to enable theteeth going past to be counted, may be provided.

The references used in FIG. 5 are the same as those used in FIG. 1, plus400. In the preceding figures, e.g. in FIG. 3, the brake release ductopens out outside the motor in a substantially radial face thereof.Thus, the duct 362 in FIG. 4 comprises a first axial segment 362Aconnected to a second segment 362B which is radial and which opens outin the brake release chamber 360. In the variant shown in FIG. 5, thebrake release duct comprises a single radial segment 462 which passesthrough the axial extension 448 of the cam 404. When the motor has astationary casing, this configuration makes it possible to simplify themachining of the brake release duct, insofar as it is possible toconnect the external brake release pipes to the end of the duct thatopens out in an axial face of the portion 402A of the casing of themotor.

FIG. 1 shows that the braking system comprises mechanical brake releasemeans which include an axial tapped hole 90 which is formed in the brakepiston 40 and which opens out in a substantially radial face of thepiston, which face is situated at the end further from the cylinderblock, i.e. at the end opposite from the first teeth 42 of the positiveclutch. The brake release means also include an axial bore 92 which isprovided in a substantially radial portion of the casing of the motorthat is situated facing the brake piston. In this example, the bore 92is provided in a portion in the form of a radial flange of thedistribution cover 2B. the bore 92 is aligned with the axial tapped hole90. In order to release the braking, a brake release screw (not shown)can be inserted through the axial bore into the tapped hole 90, and,insofar as the head of the screw is held in abutment outside the bore92, turning the screw in the tightening direction inside the tapped hole90 causes the brake piston 40 to be returned in the direction opposingthe action of the spring washer 68, i.e. in the break-releasingdirection. Under usual motor operating conditions, the bore 92 isclosed, e.g. by means of a stopper 94. Alternatively, the brake releasescrew may be pre-inserted into the bore while being held by any suitablemeans (e.g. a spacer) in a set-back position in which its free end doesnot extend beyond the end of the bore 92 that faces the tapped hole 90.The mechanical brake release means comprise at least two brake releasesets of this type, spaced apart circumferentially.

It is indicated above that the internal profile of the first couplingsegment is analogous to the reaction profile of the reaction member, andthat the external profile of the second coupling segment matches theinternal profile so as to transmit the braking torque. For example, in afirst variant, the internal profile may be identical to the reactionprofile, and the external profile may be exactly complementary to theinternal profile. When the internal and external profiles serve not onlyto pass on the braking torque but also to define the brake releasechamber, as in FIG. 1, the internal and external profiles must beexactly complementary so that sealing can be provided by means of asingle gasket which, for example, reproduces the undulations of the camand is of constant radial thickness.

It is however possible to obtain this function without the internalprofile of the first coupling segment 147 exactly extending the profileof the cam. FIG. 6 is an extremely diagrammatic section view showingsuch a possibility. In this figure, the cam surface 504 is provided, forexample, with six undulations uniformly distributed over its periphery,and formed by machining the internal periphery of the portion 502A ofthe casing. It is possible for the internal profile 550 of the firstcoupling segment to be provided with three undulations only, every otherlobe of the cam not being reproduced. The brake piston 540 has anexternal profile 554 which is exactly complementary to the profile 550,so that the two surfaces constituted by the internal profile 550 and bythe external profile 554 may be sealed by means of a gasket of constantthickness (for reasons of clarity, the gasket is not shown, and theprofiles 550 and 554 are shown spaced apart from each other). Forreasons of simplification, the internal elements of the motor such asthe distributor which is situated inside the brake piston are not shownin FIG. 6. Similarly, in the portion 502A of the casing, only the brakerelease duct 562 and the bores 503′ for the fixing screws for fixingtogether the portions of the casing are indicated.

The configuration shown in FIG. 6 is particularly advantageous because,with it being simple to machine the reaction profile and the internaland external profiles that transmit the braking torque, as well as thebrake piston, it is possible to increase the brake release surface area.This area is defined by the area of the region in which the two radialfaces (60A and 60B in FIG. 1) of the brake release chamber face eachother, these faces being respectively defined on the axial extension ofthe casing and on the brake piston. In the shaping configuration of FIG.6, the brake release area is equal to the area of the face 560B of thebrake release chamber. It can be seen that this area is significantlylarger than the brake release area that would be provided if theinternal profile were identical to the cam profile, in which case itwould be necessary to deduct from the area of the face 560B the shadedportions on FIG. 6 corresponding to half of the cam lobes. By increasingthe brake release area in this way, it is possible to increase theeffectiveness of the brake release fluid. Effective brake release canthus be obtained with a fluid pressure that is lower or, rather, greaterbrake release can be obtained for any given fluid pressure, which makesit possible to use a spring that exerts a higher force, thereby makingit possible to obtain higher braking torque.

FIG. 6 shows that the coupling profiles of the coupling collar and ofthe brake piston are advantageously formed by undulations, the troughportions of the undulations of the coupling profile of the internalcoupling face of the collar extending axially in register with at leastsome of the trough portions of the undulations of the reaction member.In other words, at least some of the cam lobes are “used” to form thecoupling profiles.

FIG. 7 shows that the casing of the motor is in three portions,respectively 602A (whose internal periphery forms the undulating cam604), 602B (distribution cover), and 602C. The portion 602C is thecoupling collar of which an axial segment forms a coupling segment 647,the internal periphery of said segment defining the internal couplingprofile 650. The brake piston 640 includes a second coupling segment 652whose external axial face 654 has the external coupling profile which,by co-operating with the profile 650, makes it possible to key thepiston so that it is prevented from rotating relative to the collar602C. The collar is disposed between the distribution cover 602B and theportion 602A of the casing that carries the cam. The collar 602C thusextends around a marginal portion of the cylinder block 606 situated onthat side of its radial face which faces the distributor 616 (on whichface the teeth 644 are situated), and around the portion of thedistributor that is adjacent to the cylinder block.

The brake piston 640 is disposed in an annular cavity 656 providedaround the distributor, substantially in the same shaping configurationas in FIG. 1.

Unlike the collar in FIG. 1, the collar 602C is not made in one piecewith the casing which carries the cam. It is constituted by a distinctpart which is fixed to the other portions of the casing by the screws603 for fixing the casing, these screws naturally being dimensioned towithstand the high torque exerted on the assembly made up of the variousportions of the casing during motor operation. While ensuring that thebraking assembly is robust, this configuration makes it possible todispose the same braking assembly on various types of motor (e.g. whichdiffer from one another by the number of cam lobes that they have, orrather, by the amplitude of their cam undulations). As in FIG. 1, thecoupling profiles of the faces 650 and 654 are advantageously formed byundulations.

As in FIG. 1, the brake release chamber 660 is formed between twostepped axial portions of the coupling collar 602C and two stepped axialportions of the piston 640. The internal periphery of the axial portion648B of the coupling collar and the external periphery of the portion640B of the piston, which peripheries co-operate with each other, may becylindrical. However, it is also possible to choose to form them inundulating manner so that they couple the piston 640 to the collar 602Cto constrain it to rotate therewith. In which case, the externalperiphery of the axial segment of the piston that is adjacent to thefirst braking means (teeth 642 provided on the piston) and the internalperiphery of the portion of the collar 602C which co-operates with saidexternal periphery may be cylindrical.

The brake release duct 662 may be may be formed in part in thedistribution cover 602B and in part in the coupling collar 602C.

FIG. 8 is an axial section view of the portion of the motor that issituated on the opposite side of the cylinder block from thedistributor. It is thus possible to see a portion of the cylinder block706, part of the casing portion 702A whose internal periphery forms thecam 704, part of another casing portion 702D which is assembled on theportion 702A by casing assembly screws 703, and a shaft 705 which isconstrained to rotate with the cylinder block 706 by any suitable means,e.g. by fluting. The shaft 705 includes a radial flange 705A which issupported to rotate relative to the internal periphery of the portion702D of the casing by a bearing 709 which is shown verydiagrammatically, it being possible for this bearing to comprise anytype of rolling members, e.g. balls or conical roller bearings. Theflange 705A of the shaft 705 is provided with tapped holes 705B whichenable it to be fixed to an object that is to be driven in rotation.

The brake piston 740 is disposed in an annular space 756 which, in thisconfiguration, is provided between the portion 702D of the casing andthe shaft 705, and which is defined axially by the radial wall of thecylinder block that is further from the distributor (not shown) and bythe substantially radial face 705C of the flange 705A that faces towardsthe radial wall of the cylinder block. The first braking means 742(first series of teeth) are integral with or secured to the active face740 of the piston, which active face faces the face 705C of the flange705A. The second braking means 744 (second series of teeth) are integralwith or secured to the said face 705C. The brake piston 740 isconstantly urged in the braking direction (i.e. away from the cylinderblock 706) by a spring 768 constituted by a Belleville spring washer.

The coupling collar is constituted by the axial segment 747 of thecasing portion 702D which is adjacent to the portion 702A. In order toconstrain the piston to rotate with the casing, the internal periphery750 of the collar and the external periphery 754 of the coupling segment752 of the piston 740 have coupling profiles that preferably formundulations. These profiles are sealed relative to each other becausethey define the brake release chamber 760. On the other side, in thevicinity of the cylinder block, the chamber 760 is defined by the facingcylindrical axial peripheries of the piston and of the casing portion702D, which peripheries are also sealed relative to each other.

FIGS. 1 to 8 shows the invention as applied to a motor having astationary casing. FIG. 9 shows that the invention also applies to amotor having a rotary casing. More precisely, the motor 801 comprises:

a rotary casing in three portions 802A, 802B, and 802C assembledtogether by screws 803;

an undulating reaction cam 804 provided on the internal periphery of theportion 802B of the casing;

a cylinder block 806 which is provided with a central bore 808 and whichis prevented from rotating about the axis 810, the cylinder blockcomprising a plurality of radial cylinders 812 suitable for being fedwith fluid under pressure, and inside which pistons 814 are slidablymounted;

an internal fluid distributor 816 constrained to rotate with the casingabout the axis 810, i.e. it rotates with the casing relative to thecylinder block, and provided with distribution ducts 818 suitable forcommunicating with the cylinders 812; and

a first central core segment 820 which is stationary and which isprovided with fluid feed and exhaust ducts 822, and a second centralcore segment 824 which, via intermediate ducts 826, puts the fluid feedor exhaust ducts in communication with grooves 828 and 830 providedbetween its external periphery and the internal periphery of the fluiddistributor 816.

The second segment 824 is secured to the first segment 820 by means ofscrews 832. The cylinder block is secured to the segments 820 and 824 sothat they are prevented from rotating by means of fluting provided inits bore 808 and co-operating with complementary fluting provided on theexternal peripheries of the segments 820 and 824. The casing issupported as it rotates by bearings 834 on the axial periphery of thecore segment 820. The distributor 816 is constrained to rotate with theportion 802C of the casing by means of a stud-and-notch system 836.

The braking system that equips the motor is analogous to the systemshown in the preceding figures, with the first coupling segment 847being provided on an axial extension of the reaction member, and thebrake piston 840 being provided with the second coupling segment 852.The braking torque is passed on, i.e. the piston and the reaction memberare constrained to rotate together, by means of the internal profile 850of the first coupling segment 847 co-operating with the external profile854 of the second coupling segment 852.

In the example shown in FIG. 9, the surfaces defined by the internal andexternal profiles also serve to define the brake release chamber 860, sothat the internal and external profiles are complementary. Naturally, itis possible to provide the variants mentioned with reference to thepreceding figures. The first braking means are constituted by a firstseries of teeth 842 which are mounted on one end of the brake piston840, while the second braking means are constituted by a second seriesof teeth 844 which are mounted on an end face 846 of the cylinder blockthat is situated under the axial extension in which the first couplingsegment is provided.

The brake release chamber 860 is fed with fluid under pressure via abrake release duct comprising a first segment 862A which is disposedaxially in the central core segment 820, a second segment 862B which isdisposed radially and which engages in this axial segment to open out inthe external axial face of the central core segment 820, and third andfourth segments 862C and 862D. An axial face formed in a transverseflange 802′A of the casing portion 802A faces that region of the axialperiphery of the core segment 820 in which the duct 862B opens out. Acommunication chamber 865 is thus provided, which chamber is sealed oneither side of the end of the duct 862B by sealing gaskets 863. The ductsegment 862C is provided in the portion 802A of the casing, and it opensout in the chamber 865 to be put permanently in communication with theduct 862B. The segment 862C is connected to the axial segment 862D whichis provided in the portion 802B of the casing, this duct 862D openingout in the brake release chamber 860. For the purpose of permanentlyurging the piston 840 in the braking direction, resilient return meansare provided, e.g. constituted by helical springs 868.

It can be noted that the external periphery of the portion 802B of thecasing is provided with two sprockets 895 and 897. These sprockets canengage with chains, thereby enabling the motor 801 to be used, forexample, for driving compact loader wheels disposed in tandem.

FIG. 10 also shows the invention as applied to a motor 901 having arotary casing. For example, in this motor, the casing carries sprockets995 and 997. The cylinder block 906 is prevented from rotating and maybe fixed to the chassis of a vehicle via a flange 906′ that is providedon it and that projects from the casing. The casing comprises a firstportion 902A which is disposed around the cylinder block, and extends tothe flange 906′, and a second portion 902B which forms the distributioncover and which may also be fixed to the chassis of the vehicle. Thecasing is supported to rotate relative to the cylinder block by rollerbearings 934, e.g. by ball bearings.

As in the motor shown in FIG. 8, the braking system is disposed on thatside of the cylinder block which is further from the distributor 916.The brake piston is formed by a shaft 940 which is provided with asubstantially radial flange 941. The shaft 940 passes through thecylinder block 906 and is provided with an end which extends into acentral axial bore of the distributor 916.

The coupling collar 947 is formed by an end portion of the portion 902of the casing and it is made integrally therewith. The portion 902Acarries the cam 904. The internal coupling surface is formed on theinternal periphery 950 of the collar. The external coupling surface 954is formed on the axial surface of the end of the flange 941. Thesesurfaces 950 and 954 have coupling profiles that are preferably formedby the undulations, which make it possible to constrain the shaft 940 torotate with the casing.

It can be noted that, at its end 940′ that extends into the distributor916, the shaft 940 is provided with fluting 940″ which co-operates withfluting 916′ in the distributor so as to constrain the distributor torotate with the shaft and thus with the casing.

The first braking means (the teeth 942) are formed on that radial faceof the flange 941 which faces the cylinder block. The second brakingmeans (the teeth 944) are formed on that radial face of the cylinderblock which faces the flange 941.

More precisely, the second braking means 944 are formed on the radialface of the end of an annular extension 970 of the cylinder block whichco-operates with the roller bearings 934. The brake release chamber 960is formed between the flange 941 and the cylinder block 906. An indent970′ is provided in the radial face of the cylinder block that isfurther from the distributor, because of the presence of the annularaxial extension 970.

The flange 941 is provided with a setback 941′ which penetrates in partinto the indent 970′. The internal periphery of the annular extension970 and the external periphery of the setback 941′ extend axially andare sealed relative to each other by gaskets 966. This configurationmakes it possible for the piston 940 to slide axially relative to thecylinder block while defining the chamber 960.

A brake-release duct 962 which opens out in the distribution cover 902Bmakes it possible to feed the chamber 960. The brake release duct opensout in the central bore of the distributor which, naturally, is sealedrelative to the outside and, insofar as the shaft 940 is not sealedrelative to the central bore of the cylinder block (one or morecommunication bores may even be provided), it thus makes it possible tofeed the chamber 960 which is permanently in communication with theannular bore of the distributor.

An annular space 975 is provided between the shaft 940 and the bore 976in the cylinder block in which it is inserted. A helical spring 968 isdisposed in the annular space, in which it abuts between firstly aradial wall 976′ of the bore 976 and secondly a flange 943 which iskeyed on the shaft 940, e.g. by a spring clip. The helical springconstantly returns the brake piston in the braking direction.

In any of the above-described embodiments, the brake release chamber maybe formed between a first axial portion of the piston and a facing firstaxial portion of the coupling collar, having coupling undulations, and asecond axial portion of the piston and a facing second axial portion,also having undulations, the second axial portions being offset relativeto the first axial portions.

What is claimed is:
 1. A hydraulic motor comprising: a casing; areaction member integral with or secured to the casing and having aninternal periphery that defines a reaction profile; a cylinder blockwhich is mounted so that the cylinder block and the reaction memberrotate relative to each other about an axis of rotation, the cylinderblock comprising a plurality of piston-and-cylinder sets comprisingcylinders and pistons, disposed radially relative to the axis ofrotation and suitable for being fed with fluid under pressure; aninternal fluid distributor constrained to rotate with the casing aboutthe axis of rotation, and provided with distribution ducts that can putthe cylinders in communication with fluid feed and exhaust ducts; and abraking system comprising first and second braking means constrained torotate respectively with the casing and with the cylinder block aboutthe axis of rotation, a brake piston having a substantially radialactive braking face to which a brake member is secured, said pistonbeing suitable for taking up both a brake-releasing position and abraking position in which said piston urges the first and second brakingmeans into braking engagement so as to prevent the cylinder block andthe casing from rotating relative to each other, and means fordisplacing the brake piston between said braking and brake-releasingpositions; said brake piston being constrained to rotate with the casingabout the axis of rotation and the brake member which is secured to theactive braking face of said piston being a first brake member belongingto the first braking means.
 2. A motor as claimed in claim 1, includinga coupling collar which forms a portion of the casing and which has aninternal axial face with which an external axial face of the brakepiston co-operates to key said piston so that the latter is constrainedto rotate with the casing, said internal and external axial faces havingcoupling profiles suitable for this purpose.
 3. A motor according toclaim 2, wherein the coupling collar is constituted by an axialextension of the reaction member, which extension is integral with saidreaction member.
 4. A motor as claimed in claim 2 or 3, wherein thereaction profile of the reaction member is formed by undulations, andwherein the coupling profiles are also formed by undulations, the troughportions of the undulations of the coupling profile of the internalcoupling face extending axially in register with at least some of thetrough portions of the undulations of the reaction member.
 5. A motor asclaimed in claim 1, wherein a second brake member belonging to thesecond braking means is integral with an end face of the cylinder blockwhich extends facing the active face of the brake piston.
 6. A motor asclaimed in claim 1, wherein a second brake member belonging to thesecond braking means is secured to an end face of the cylinder blockwhich extends facing the active face of the brake piston.
 7. A motor asclaimed in claim 1, wherein a second brake member belonging to thesecond braking means is integral with a flange which equips a shaftkeyed so that it is prevented from rotating relative to the cylinderblock.
 8. A motor as claimed in claim 1, wherein the first and secondbraking means respectively comprise a first series of positive clutchteeth and a second series of positive clutch teeth, the first series ofteeth being integral with the active face of the brake piston.
 9. Amotor as claimed in claim 8, including a coupling collar which forms aportion of the casing and which has an internal axial face with which anexternal axial face of the brake piston co-operates to key said pistonso that the latter is constrained to rotate with the casing, saidinternal and external axial faces having coupling profiles suitable forthis purpose, wherein the brake release chamber is formed between twostepped axial portions belonging to the coupling collar, and two steppedaxial portions belonging to the brake piston, a first sealing gasketbeing disposed between the first axial portion of the collar and thefacing first axial portion of the brake piston, while a second sealinggasket is disposed between the second axial portion of the collar andthe facing second axial portion of the brake piston.
 10. A motor asclaimed in claim 9, wherein the axial portions of the coupling collarand of the brake piston between which the brake release chamber isprovided are annular, the first axial portion of the collar beingconnected to the coupling internal axial face of said collar via asetback, while the first axial portion of the brake piston is connectedto the coupling external axial face of said piston via a shoulder.
 11. Amotor as claimed in claim 9, wherein the coupling internal axial faceand the coupling external axial face are respectively formed on thefirst axial portion of the coupling collar and on the first axialportion of the brake piston, and wherein the coupling profiles areundulating profiles.
 12. A motor as claimed in claim 1, wherein thefirst and second braking means respectively comprise a first series ofpositive clutch teeth and a second series of positive clutch teeth, thefirst series of teeth being secured to the active face of the brakepiston.
 13. A motor as claimed in claim 1, wherein the means fordisplacing the brake piston between the braking position and thebrake-releasing position comprise a brake release chamber suitable forbeing fed with fluid under pressure, said chamber having a substantiallyradial wall which is formed by a face of the position that faces thesame way as the active face of said position, and which is offsetaxially relative to said active face.
 14. A motor as claimed in claim 1,wherein the braking system comprises mechanical brake release meanshaving at least two sets, each of which includes an axial tapped holeprovided in the brake piston and opening out in a substantially radialface of the piston, which face is opposite from the first braking means,and an axial bore provided in a substantially radial portion of thecasing, which portion is situated facing the brake piston and alignedwith the axial tapped hole of said piston, each of said sets furtherincluding a brake release screw suitable for being inserted through theaxial bore in the casing and into the axial tapped hole in the brakepiston.
 15. A motor as claimed in claim 1, wherein the first and secondbraking means respectively comprise a first series of positive, clutchteeth and a second series of positive clutch teeth, the motor includingmeans for measuring a speed of rotation thereof, which means comprise aspeed detector received in an element of the stator of the motor andfacing that one of the first and second series of teeth which isconstrained to rotate with the rotor of the motor.
 16. A motor asclaimed in claim 1, provided with a through axial passageway which isdefined in the region of the distributor by a hollow cylindrical sleevewhose first axial end situated on a first side of the distributor isconnected in sealed manner to the wall of a through axial bore providedin the cylinder block and aligned with the sleeve, and whose secondaxial end situated on the other side of the distributor is connected insealed manner to the wall of a through axial bore in the casing.